This invention relates to flexible electro-optic displays, in particular to displays based on flexible fabrics and other flexible permeable materials.
An electro-optic display is a device that changes its optical state when electric or electromagnetic signals are applied to it. The display may change as a whole unit or in parts constituting a visible image. The image on such displays is formed from a plurality of display elements including an electro-optically active (EOA) substance. xe2x80x9cEOA substancexe2x80x9d shall mean here a substance that changes its color, transparency, reflectivity or other optic properties, or emitting light, when subjected to changes of electric or electromagnetic field.
Flexible electro-optic displays may be made of flexible polymer films, where the EOA substance and patterns of electrodes are laid in thin layers over a polymer substrate, or may be based on flexible fibers or strips woven or knitted into fabric or textile material where the electrodes are in the constituent fibers. Woven displays have certain advantages since they may be produced using known weaving techniques which do not limit their length. Woven displays are more flexible and robust than integral film displays.
U.S. Pat. No. 5,962,967 and JP 2001-034195 disclose woven displays made of two sets of transverse fibers, each fiber including a longitudinal conductor, and at least fibers of one set including a coating of light-emitting or other EOA substance. At each junction where a fiber of one set overlaps a fiber of the other set, an EOA zone is formed from the EOA substance between the fibers. Each EOA zone is an individually controllable display element (pixel). The visible images are formed from a plurality of such pixels. The EOA zones (pixels) in such displays are of the size of the fiber diameter.
WO 99/19858 describes a woven display produced from flat fibers or strips in basket weave. The display comprises two intersecting sets of stripes. One of these sets may consist of display stripes with electroluminescent layer, while the other set consists of conductive stripes, or both sets may comprise display stripes and conductive stripes. The display stripes have a back conductive layer laid in separated areas defining display elements (pixels). The pixels effectively use the entire area of the applied electroluminescent layer.
U.S. Pat. No. 6,229,265 discloses a rigid electroluminescent display with display elements of EOA substance laid in grooves. The grooves are made in a common base electrode while individual electrodes are very narrow strips integral with a transparent layer covering the base electrode and the EOA substance.
In accordance with one aspect of the present invention, there is provided an electro-optical display comprising a flexible three-dimensional structure including at least two layers of electrode structures, which are held together but spaced apart by at least one skeletal layer formed of fibers transverse to the layers of electrode structures. The skeletal layer has empty space among the transverse fibers, filled with an electrooptically active (EOA) substance, whereby an electrooptically active zone (EOA zone) is formed by the EOA substance between the electrode structures. The 3D structure preferably comprises network layers made of fibers, or flexible film layers which carry the electrode structures, and are secured to the fibers of the skeletal layer.
The network layers may be formed of a plurality of woven or knitted fibers, or of a plurality of overlapping (non-woven) fibers. Hereinafter, a xe2x80x9cfiberxe2x80x9d shall mean any elongated and flexible element capable of being woven or knitted or sewn. A fiber may have round, flat, or other cross-section form. The electrode structures may be formed of flexible conductive layers or of conductive fibers. Hereinafter, a xe2x80x9cconductive fiberxe2x80x9d shall mean any elongated flexible element suitable for conducting electricity. For example, it may have round, flat or other section form; be made of solid metal; be in the form of a dielectric fiber or strip covered or intertwined with a conductive wire or layer; multiple-core twisted, spun, plaited wire; etc.
The network layers of the flexible 3-D display structure of the present invention may be made of a plurality of woven or knitted fibers, where in each network layer are interwoven non-conductive fibers protruding from one or both sides thereof in the form of Velcro hooks and loops or plush pile, and the skeletal layer is formed by the hooks and loops or the pile of two network layers snapped together.
In the electro-optical display of the present invention, the EOA zone may comprise a plurality of distinctive display elements constituting an image. According to one embodiment, the display elements are formed by separated areas of EOA substance or by areas of EOA substance with different electro-optic properties. According to another embodiment, a first electrode structure is formed from separated areas with individual wiring, and these areas, together with a second electrode structure, constitute display elements.
According to still another embodiment of the invention, the electrode structures are made of sets of conductive fibers interwoven with the network layers which are made of woven or knitted fibers. One electrode structure may comprise a first set of parallel conductive fibers, and another electrode structure may comprise a second set of parallel conductive fibers transverse to the first set. Thereby the EOA zone is constituted by a matrix of individually controllable EOA zones (pixels), each defined in the overlapping of a conductive fiber of the first set with a conductive fiber of the second set.
According to a further embodiment of the invention, the electrode structure may further comprise a conductive transparent or translucent layer in contact with the set of parallel conductive fibers. This layer may be in the form of separated strips parallel to the conductive fibers, each strip being in contact with at least one conductive fiber; or the layer may be continuous but of predetermined limited conductivity, such that the effective electric field of each conductive fiber is expanded over a strip of predetermined width disposed along said fiber. When a second conductive layer is applied to a second transverse electrode structure in a similar manner, a matrix of individually controllable enlarged pixels is formed, each pixel being defined in an overlapping of two transverse strips.
According to another aspect of the present invention, there is provided a three-dimensional spacer fabric comprising at least two woven or knitted network layers spaced by a skeletal layer made of non-conductive fibers predominantly transverse to and interwoven with the network layers, wherein the network layers comprise conductive fibers. The conductive fibers in one network layer may be arranged in a conductive network or in a set of parallel fibers. The two network layers may have transverse sets of parallel fibers adapted for forming a matrix structure. Each network layer may further comprise a second set of conductive fibers transverse to and in contact with the first set of parallel conductive fibers, where the fibers of the second set have a lower predetermined conductivity than the fibers of the first set and play the role of the above-mentioned layer with limited conductivity.
The 3-D structure of the present invention can be easily produced by known warp-knitting process. Not only the 3-D structure but also the electrode structure may be manufactured in the same time by the same process. The present invention allows for the manufacture of multi-layered 3-D display structures which can be used i.e. for two-sided displays. The EOA substance is very reliably accommodated in the skeletal layers of the structure due to the numerous surfaces of contact and adhesion. The thickness of the skeletal layer and hence of the EOA layer is not limited by the thickness of the constituent fibers as in the prior art. The electrode structures are reliably kept at predetermined distance from each other thus preventing electrical breakdown of the display.